Parameter identification and pileup behavior of TiAl alloy through nanoindentation and crystal plasticity simulation

In this work, the load-displacement curves of γ and B₂ phases in Ti-43.5Al-4 Nb-1Mo-0.1B (TNM) alloy were obtained from nanoindentation experiments and corresponding crystal plasticity finite element (CPFE) simulations. The good consistency of constitutive curves and the small error of hardness between experiments and simulation results confirmed that the constitutive parameters of γ and B₂ phase in TiAl alloy could be well verified by nanoindentation. Based on nanoindentation tests and CPFE simulation, the pileup morphology of each grain around the indents has been systematically discussed. The pileup morphology is closely related to the slip behavior around the indents, which could be analyzed by the calculation of Schmid factors, including surface Schmid factor (SSF) and interior Schmid factor (ISF). Results show that a large SSF and a small ISF will promote the accumulation of cumulative shear strain at the surface of the materials, further facilitating the pileup profile. Besides, the pileup morphology is closely related with the movement of dislocation, which greatly influences the flow ability of the material, further altering the height of pileup profiles.